Temperature-Inert Coinage Metal Cluster Scintillator

Scintillators can convert high-energy ionizing radiation, such as X-ray, into low-energy ultraviolet-visible photons, and they have been widely used in various fields. However, like most luminogens, the emission intensity of a scintillator is usually influenced by the environmental temperature, increasing the temperature results in extreme decreases in radioluminescence. Here, a temperature-inert coinage metal cluster scintillator of Cu₄S was prepared, and it exhibited not only intense radioluminescence at room temperature but also minimal fluctuations from 80 to 450 K. Mechanism study revealed that Cu₄S is a typical thermally activated delayed fluorescence (TADF) luminogen. Owing to the strong C─H···π interactions between the clusters, the geometric relaxation of Cu₄S was restricted during the spin crossover process, leading to an exceptionally small reorganization energy. This induced intersystem crossing within the Marcus inverted region, resulting in temperature-independent luminescence behavior. More importantly, Cu₄S metal cluster has excellent water‒oxygen stability and thermal stability and can be used to prepare flexible scintillator screen with polydimethylsiloxane (PDMS). On the basis of these features, temperature-independent high-resolution X-ray imaging with the Cu₄S-PDMS scintillator screen was achieved, and the resolution at different temperatures was maintained above 20 LP mm^-1.